Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS AND METHOD FOR DESIGNATING FRAME OFFSET
OF SUPPLEMENTAL CHANNEL
IN A CDi\IA COMMUNICATION SYSTEI\'I
BACKGROUND OF THE INVENTION
1. F_ieldof the Invention
The present invention relates generally to a communication apparatus and
method for a CDMA mobile communication system, and in particular, to an
apparatus
and method for assigning a supplemental channel in a CDMA mobile communication
system.
2. De_scr_iption of the Related Art
In general, a CDMA (Code Division Multiple Access) mobile communication
system assigns (or designates) different frame offsets to the users so as to
distinguish the
transmission frames to the respective users.
In the conventional CDMA mobile communication system. one 20ms frame is
equally divided into 16 1.2~ms segments, to which different frame offsets are
assigned
according to the users. A data frame is transmitted/received at a time point
delayed by a
frame offset assigned to the corresponding user on the basis of the system
time.
In a voice call, the frame offset contributes to dispersion of a load. When
many
2~ users simultaneously intend to transmit data at a boundary of the 20ms
frame, there is a
case where it is not possible to simultaneously process all the user frames.
In this case, the
frame processing time is delayed in a channel card, a base station controller
and a voice
codec (or vocoder). This delay is a main factor in quality deterioration of a
voice service.
Therefore, the 20ms frame is equally divided into 16 segments, and then, the
divided
segments are uniformly distributed to the users so that the load should be
naturally
dispersed using the reference time delayed by the corresponding frame offset
between the
base station and the mobile station.
Although the conventional CDMA mobile communication system has chiefly
provided a voice service, a future CDMA mobile communication system will
provide a
high-speed data service as well as the voice service. The future CDMA mobile
communication system is normally called an IMT-2000 mobile communication
system.
The IMT-2000 mobile communication system can provide new services such as a
high-
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quality voice service, a moving picture service, and an Internet search
service.
In the conventional voice service, loads are uniformly generated at regular
intervals. Therefore. in the voice service, the users uniformly dispersed over
the frame
offsets can process the voice data without delay. However, the future CDMA
mobile
communication system, which chiefly provides a multimedia service, generates
data
which has different features from the existing voice data. That is, the data
having the
different features may be packet data. In many cases, the packet data is
generated at a
burst. Therefore, the packet data has a feature that a large amount of data is
generated at a
short time, rather than a specific amount of data being consecutively
generated.
When a traffic having this feature is generated, the system assigns a
supplemental charmel (SCH) in addition to a fundamental channel (FCH). The
newly
added supplemental channel uses the same frame offset as the previously
connected
fundamental charmel.
When it is necessary for several users assigned the same frame offset to
transmit
a great amount of data at a high data rate, there may occur a state where the
amount of the
transmission data exceeds a traffic capacity in which the data can be
transmitted at the
corresponding frame offset without delay. In this case, a call is set up using
only an initial
fundamental channel, and each user is assigned a unique frame offset for the
initial
fundamental channel.
At this moment, several users may have the same frame offset. As a result,
there
may occur a situation where the traffic exceeds a capacity of a link between a
base station
and a base station controller at a specific frame offset. This will cause a
delay in
transmitting the data. In a service of which quality is affected by the delay,
such as the
voice service using the fundamental channel, the delay of the data
deteriorates the service
quality.
On the other hand, the supplemental channel can be used in several methods. In
general, the CDMA mobile communication system assigns different supplemental
channels to the respective users. In this case, the future CDMA mobile
communication
system can assign a supplemental channel as a new traffic is generated in a
state (or a
traffic state) where a basic call is connected. Here, the "traffic state"
refers to a traffic
channel-established state. In this case, a service delay problem and a
scheduling loss
problem may occur because the supplemental channels are fixedly assigned to
the users.
Furthermore, in the future high-speed communication system, several users may
use a
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limited number of the supplemental channels on a time-division basis, rather
than using
the supplemental channels uniquely assigned to the users. However, this may
cause a
scheduling loss problem because the users have the different frame offsets.
$ SUMMARY OF THE INVENTION
15
2~
It is, therefore, an object of the present invention to provide a channel
assignment apparatus and method for designating a frame offset upon receipt of
a data
transmission request in a traffic state, in a CDMA communication system.
It is another object of the present invention to provide an apparatus and
method
for assigning a supplemental channel by designating a frame offset of the
supplemental
channel upon receipt of a data transmission request in a traffic state in a
CDMA
communication system.
It is further another object of the present invention to provide an apparatus
and
method for designating new frame offset information such that a base station
can assign a
supplemental channel by designating a frame offset of the supplemental channel
upon
receipt of a data transmission request in a traffic state, in a CDMA
communication system.
It is yet another object of the present invention to provide an apparatus and
method in which a mobile station designates a frame offset of a supplemental
channel by
receiving the frame offset information from the base station upon receipt of a
data
transmission request in a traffic state in a CDMA communication system.
It is still another object of the present invention to provide an apparatus
and
method for assigning a new frame offset for a supplemental channel in a
handoff state in a
CDMA communication system.
It is still another object of the present invention to provide an apparatus
and
method for assigning a new frame offset for a supplemental channel when it is
desired to
hand off a supplemental channel in a handoff state, in a CDM A communication
system.
It is still another object of the present invention to provide an apparatus
and
method for assigning a supplemental channel by designating a new frame offset
when it is
desired to newly assign a supplemental channel in a handoff state, in a CDMA
communication system.
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It is still another object of the present invention to provide an apparatus
and
method for designating new frame offset information such that a base station
can assign
or hand off a supplemental channel by designating a frame offset of the
supplemental
channel in a handoff state, in a CDMA communication system.
It is still another object of the present invention to provide an apparatus
and
method in which a mobile station designates a frame offset of a supplemental
channel by
receiving the frame offset information from the base station in a handoff
state in a CDMA
communication system.
To achieve the above and other objects, there is provided an apparatus for
receiving data transmitted over fundamental channels having a predetermined
frame
offset for a plurality of mobile stations and supplemental channels assigned
in association
with the fundamental channels. In the apparatus, a timing generator receives a
frame
offset of the fundamental channel, a frame offset of the supplemental channel
and a
system time, outputs the system time delayed by the frame offset of the
fundamental
channel as a fundamental channel boundary signal, and outputs the system time
delayed
by the frame offset of the supplemental channel as a supplemental channel
boundary
signal. A first symbol combiner combines mufti-path symbols transmitted over
the
fundamental channel. A second symbol combiner combines mufti-path symbols
transmitted over the supplemental channel. A first deinterleaver receives the
symbols and
the fundamental channel boundary signal from the first symbol combiner, and
deinterleaves the symbols from the first symbol combiner in a frame unit
determined by
the fundamental channel boundary signal. A second deinterleaver receives the
symbols
2~ and the supplemental channel boundary signal from the second symbol
combines, and
deinterleaves the symbols from the second symbol combines in a frame unit
determined
by the supplemental channel boundary signal.
Preferably, the timing generator comprises a first delay for receiving the
frame
offset of the fundamental channel and the system time, and delaying the system
time by
the frame offset of the fundamental channel to output the fundamental channel
boundary
signal; and a second delay for receiving the frame offset of the supplemental
channel and
the system time, and delaying the system time by the frame offset of the
supplemental
channel to output the supplemental channel boundary signal.
Preferably, the frame offset of the fundamental channel is different from the
frame offset of the supplemental channel.
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Preferably, the frame offset of the supplemental channel is designated
according
to an amount of the transmission data for the respective frame offsets of the
supplemental
channels assigned in association with the fundamental channels.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of the present invention
will become more apparent from the following detailed description when taken
in
conjunction with the accompanying drawings in which:
FIG. 1 is a flow diagram illustrating a general procedure for assigning a
supplemental channel in a CDMA communication system;
FIG. 2 is a flow chart illustrating a procedure added to designate a frame
offset
of a supplemental channel while assigning a supplemental channel in a CDMA
communication system according to an embodiment of the present invention;
FIG. 3 is a diagram illustrating a field definition of an extended
supplemental
channel assignment message (ESCAM) to which the frame offset-related fields
for the
supplemental channel are newly added;
FIG. 4 is a block diagram illustrating a demodulator for a receiver in a CDMA
commumcatton system;
FIG. ~ is a block diagram illustrating a combiner in the demodulator in a CDMA
communication system according to an embodiment of the present invention;
FIG. 6 is a block diagram illustrating a timing generator in the combiner of
FIG.
J;
FIG. 7 is a flow diagram illustrating a call setup procedure in a CDMA
2~ communication system;
FIG. ~ is a flow chart illustrating a procedure added to designate a frame
offset
of the supplemental channel in a service negotiation process in a CDMA
communication
system according to an embodiment of the present invention;
FIG. 9 is a flow diagram illustrating a handoff procedure in a CDMA
communication system according to an embodiment of the present invention;
FIG. 10 is a flow chart illustrating a procedure for designating a frame
offset of a
supplemental channel during a handoff in a CDMA communication system according
to
an embodiment of the present invention; and
FIG. 11 is a diagram illustrating a field definition of an extended
supplemental
channel assignment message or a universal handoff direction message, to which
a non
negotiation service configuration record field is added according to an
embodiment of the
present invention.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A preferred embodiment of the present invention will be described herein below
with reference to the accompanying drawings. In the following description,
well-known
functions or constructions are not described in detail since they would
obscure the
invention in unnecessary detail.
The present invention is to be applied to a future CDMA mobile communication
system. Therefore, although the present invention will be described herein
with reference
to the American CDMA-2000 system, it is also possible to apply the invention
to the
European UMTS system.
The present invention proposes an apparatus and method for additional
assigning
of a supplemental channel for data transmission, upon receipt of a high-speed
data
transmission request in a traffic state (or a traffic channel-established
state) bet<veen the
base station and the mobile station in a CDMA mobile communication system.
More
specifically, the apparatus and method properly designates a frame offset of
the
supplemental cham~el according to an amount of transmission/reception data for
the
respective frame offsets. To this end, a CDMA communication system according
to an
embodiment of the present invention additionally assigns a supplemental
channel upon
receipt of a high-speed data transmission request in the traffic state between
the base
station and the mobile station. At this point, a frame offset of the
supplemental channel is
properly established according to an amount of the transmission/reception data
for the
respective frame offsets presently in use. In this case, the supplemental
channel can be
designated (or assigned) the different frame offset from the frame offset of
the presently
used fundamental channel. Alternatively, the supplemental channel can be
designated the
same frame offset as the frame offset of the fundamental channel. When the
fundamental
channel and the supplemental channel are designated the different frame
offsets, several
users assigned the same frame offset can simultaneously transmit data at a
high data rate.
The base station then sends information for designating a new frame offset to
the mobile
station thrOllgh an extended supplemental channel assignment message. Upon
receipt of
the frame offset information from the base station, the mobile station
additionally
designates a frame offset for the supplemental channel in addition to a frame
offset for the
fundamental channel, thereby making it possible to operate the different frame
offsets in
the fimdamental channel and the supplemental channel.
FIG. 1 shows a general procedure for assigning a supplemental channel in a
CDMA communication system. Specifically, FIG. 1 shows a message exchange
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procedure between modules in the mobile station and modules in the base
station.
Referring to FIG. l, the mobile station includes a service option for driving
an
application service, a message processor SIG for processing a channel
establishment-
s related control message, and a resource controller (RC) for managing and
controlling base
station resources. A structure of the base station is similar to the stmcture
of the mobile
station. That is, the base station also includes a service option for driving
an application
service, a message processor SIG for processing a channel establishment-
related control
message, and a resource controller (RC) for managing and controlling logical
and
physical resources of the mobile station.
Now, a procedure for assigning a supplemental channel will be described with
reference to FIG. 1. When the mobile station has user data to transmit, the
service option
checks a size (or amount) of the data and determines whether it is necessary
to assign a
supplemental channel. If it is determined that it is necessary to assign a
supplemental
channel, the service option sends a supplemental channel assignment request
signal
Data TY-SCH.Req to the resource controller (RC) in step 110. The resource
controller
then sends a supplemental channel assignment approval signal SCH Assign.Req to
the
message processor SIG in step 120. The message processor SIG sends a
supplemental
channel request message (SCRM) to the base station in step 130.
When the base station receives the supplemental channel request message
transmitted from the mobile station, the message processor SIG in the base
station
inquires of the resource controller (RC) in the base station whether it is
possible to assign
the supplemental channel requested by the mobile station, in step 140 (SCH
Assign.Ind).
If it is possible to assign the supplemental channel, the resource controller
informs the
service option, an application service layer of the base station, that a data
transmission
request has been received from the mobile station, in step 150. Upon receipt
of the data
transmission request, the service option, which is the application service
layer, performs
several data reception processes.
In step 160, the service option of the base station performs an operation in
response to the data transmission request. The operation of the step 160 can
be separately
described for one case where the data transmission request is originated by
the mobile
station and another case where the data transmission request is originated by
the base
station. When the data transmission request is originated from the mobile
station, the base
station sends the resource controller a ready-to-receive signal Data Rx-
SCH.Res, in step
160. In the case where the data has previously been transmitted/received over
the
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fundamental channel, it is not necessan~ to send the ready-to-receive signal
to the
resource controller. On the contray. when the data transmission request is
originated by
the base station, the base station sends the resource controller a forward
supplemental
channel assignment request signal Data_TySCH.Req in step 160.
Upon receipt of the ready-to-receive signal Data Rx-SCH.Res or the data
channel assignment request signal Data Tx SCH.Req from the service option, the
resource controller determines whether it is possible to assign a reverse or
forward
supplemental channel. In this process, the embodiment of the present invention
adds a
procedure for re-designating a requested frame offset. The added procedure
includes a
process for establishing a new frame offset having a lower load out of the
parameters
required in assigning the supplemental channel. This procedure will be
described later in
detail with reference to FIG. 2. Thereafter, in step 170, the resource
controller sends the
message processor a message SCH-Assian.Res indicating whether to approve the
reverse
or fomvard supplemental channel. If assignment of the supplemental channel for
transmitting data is approved, the message processor SIG sends an extended
supplemental
channel assignment message (ESCAM) to the mobile station in step 180.
Upon receipt of the extended supplemental channel assignment message
transmitted from the base station, the message process SIG in the mobile
station sends a
control signal SCH Assign.Conf to the resource controller in step 190. At this
moment,
the resource controller assigns a transmission channel or a reception channel
of the
corresponding supplemental channel. Finally, after completing assignment of
the
supplemental channel, the resource controller sends to the service option,
which is the
application service layer of the mobile station, a data transmiv'receive
possibility
conformation message Data-Tx-SCH.conf or Data Rx-SCH.Conf in step 195. After
performing the above procedure, the base station and the mobile station
exchange a data
traffic over the additionally assigned supplemental channel.
FIG. 2 shows a procedure for assigning a frame offset for a supplemental
channel
according to an embodiment of the present invention, performed in the
supplemental
channel assignment process of FIG. 1. In FIG. 2, operations of steps 210-250
correspond
to the operations of steps 1=10-170 in FIG. 1 are performed by the base
station. Further,
operations of steps 260-29~ correspond to the operations of steps 180-19~ in
FIG. 1 are
performed by the mobile station. The procedure for assigning the frame offset
for the
supplemental channel by the base station is performed through the steps 140-
180 of FIG.
1, and the procedure for assigning the frame offset for the supplemental
channel by the
mobile station is performed through the steps 110, 120, 130, 190 and 19~ of
FIG. I .
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If a supplemental channel request message (SCRiI~I) is received from the
mobile
station or a supplemental channel assignment message is received from the
application
service layer of the base station as the application service layer has traffic
data to transmit,
the resource controller checks the present capacity of the base station in
step 220 to
determine whether the physical/logical resources are available, to thereby
decide whether
it is possible to assign the additional reverse or forward supplemental
channel. If
assignment of the supplemental channel is not permissible, the resource
controller
proceeds to step 230 where the resource controller transmits the data traffic
over the
previously connected fundamental channel (FCH) or a dedicated control channel
(DCCH),
or awaits a next command while delayinG transmission of the data traffic.
Otherwise, if assignment of the supplemental channel is permissible in step
220
or a supplemental channel request message (SCRM) is received from the mobile
station,
1 ~ the resource controller proceeds to step 240 where the resource controller
designates a
frame offset available for the supplemental channel, provides this information
to the
message processor, and further, provides information about the frame offset
for the
supplemental channel to the physical layer. The physical layer then sets this
value as an
exclusive frame offset for processing the supplemental channel. Here, for the
frame offset
of the supplemental channel established for data transmission. a proper frame
offset can
be designated according to the amount of the transmission,%reception data for
the
respective frame offsets. The frame offset can be set to be different from the
frame offset
of the fundamental channel, alternatively, the frame offset can be set to be
identical to the
frame offset of the fundamental channel. Here, the frame offset of the
supplemental
channel can be either previously set or generated by the base station through
a separate
operation. In the frame offset designation process, the resource controller
should set a
proper frame offset value such that the loads are properly dispersed to
transmit the data
without delay. Thereafter, in step 250, the resource controller generates an
extended
supplemental channel assignment message (ESCAM) to which the frame offset-
related
fields for the supplemental channel are added, and sends the Generated
extended
supplemental channel assignment message to the mobile station.
Upon receipt of the extended supplemental channel assignment message from
the base station, the message processor in the mobile station analyzes the
received
extended supplemental channel assignment message and provides the analyzed
results to
the resource controller in the mobile station, in step 260. In this process,
the message
processor sends to the resource controller the information about whether the
frame offset
for the supplemental channel is designated, and its corresponding value,
together with
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other supplemental channel parameters. Upon receipt of the analyzed results
from the
message processor, the resource controller determines in step 270 whether the
frame
offset of the supplemental channel is designated or not. If the frame offset
of the
supplemental channel is designated, the resource controller sets a frame
offset for the
supplemental channel according to the value in step 280. After setting the
frame offset for
the supplemental channel, or if the frame offset of the supplemental channel
is not
designated, the resource controller sends to the physical layer new frame
offset
information together with a supplemental channel assignment signal, in step
290. Upon
receipt of the supplemental channel-related signal from the resource
controller, the
physical layer assigns a supplemental channel and additionally sets a frame
offset for the
supplemental channel so as to enable data transmissionlreception. When the
reverse or
forward supplemental channel is established between the base station and the
mobile
station in the above method, the data traffic is transmitted to the
application service in
step 29~.
In the embodiment of the present invention, the base station includes a step
(a) in
which the resource controller of the base station determines whether the
supplemental
channel is available; a step (b) in which if the supplemental channel is
available, the
resource controller determines a frame offset to be exclusively used for the
supplemental
channel; a step (c) in which the resource controller creates the extended
supplemental
channel assignment message shown in FIG. 3 to transmit the frame offset
information to
the mobile station; and a step (d) in which the resource controller designates
the frame
offset assigned by the physical layer to the supplemental channel. Here, in
the step (d), the
resource controller should set a proper value such that the loads should be
properly
dispersed to transmit the data without delay.
In addition, the mobile station includes a step (a) for detecting a frame
offset for
the supplemental channel in the process of analyzing the extended supplemental
channel
assignment message and providing the detected frame offset information to the
resource
controller; a step (b) in which the resource controller provides the set value
to the physical
channel; and a step (c) in which the physical layer newly sets the frame
offset during
assignment of the supplemental channel.
FIG. 3 shows a structure of an extended supplemental channel assignment
message (ESCAM) to which the frame offset-related fields for the supplemental
channel
are newly added.
In the extended supplemental channel assignment message as shown in FIG. 3,
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the fields for assigning the frame offset for the supplemental channel include
a
REV-SCH FRAME_OFFSET INCL field indicating whether to newly designate a
frame offset during assignment of the reverse supplemental channel, and a
REV SCH FRAME OFFSET field for actually designating a new frame offset. The
fields further include FOR SCH FRAME OFFSET INCL and
FOR SCH FRAME OFFSET fields indicating whether the frame offset is designated
during assignment of the forward supplemental channel and the designated
value,
respectively. In the existing system, the supplemental channel is also
assigned the same
value as the frame offset designated during assignment of the fundamental
channel of the
dedicated control channel. However, in the embodiment of the present
invention. the
REV SCH FRAME OFFSET and FOR SCH FRAME OFFSET field values are
designated such that one of 16 frame offsets should be designated within 20ms
during
assignment of the supplemental channel, thereby making it possible to
designate the
frame offsets in a unit of 1.2~ms.
FIG. 4 shows a demodulator for a receiver in a CDMA communication system.
Referring to FIG. 4, reference numeral 400 indicates an antenna of the mobile
station for receiving various input signals. Reference numeral 410 indicates
correlators
for separating the multi-path signals received through the antenna 400.
Reference numeral
420 indicates a combiner for combining the separated multi-path signals into
one signal.
The combined signal output from the combiner 420 is applied to deinterleavers
430, and
the output signals of the deinterleavers 430 provided to decoders 440. The
combiner 420
provides a frame boundary indication signal to the deinterleavers 430 through
a control
line 450 in addition to the combined symbols.
In operation, the correlators 410 detect correlation values of the associated
multi-
path signals, and the combiner 420 combines the correlation values output from
the
correlators 410. Further, the combiner 420 generates a signal for
distinguishing a frame at
a frame boundary. In the embodiment of the present invention, since the frame
offset
value of the fundamental channel is set to be different from frame offset
value of the
supplemental channel, the combiner 420 generates the frame boundary signals of
the
fundamental channel and the supplemental channel at the different time points.
The
detailed description of the frame boundary signals will be made with reference
to FIG. ~.
The deinterleavers 430 receive the frame boundary signals from the combiner
420 through the control line 4~0, and deinterleave the symbols output from the
combiner
420 in a frame unit. Here, the frame boundary signals output through the
control line 450
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include an FCH/DCCH frame boundary signal and an SCH frame boundary signal.
The
decoders 440 decode the symbols output from the deinterleavers 430 to create
decoded
data.
J FIG. ~ shows a detailed structure of the combines 420 of FIG. 4
Referring to FIG. ~. the combines 420 includes a timing Generator 540, a first
symbol combines 5~0 for combining FCH/DCCH symbols, and a second symbol
combines ~~~ for combining SCH symbols. The timing generator 340. receiving a
system
time, sets frame boundaries. generates corresponding frame boundary signals at
the set
frame boundaries, and provides the generated frame boundary signals to first
and second
deinterleavers 431 and 43~. Since the embodiment of the present invention sets
the frame
offset of the supplemental channel at the point where the supplemental channel
is
assigned, the fundamental channel and the supplemental channel can use the
different
1 ~ frame offsets. Therefore, the timing generator 540 generates a first frame
boundary signal
for FCH/DCCH through a control line 363 and a second frame boundary signal for
SCH
through a control line 560, depending on the system time, the FCH/DCCH frame
offset
value and the SCH frame offset value. That is, when it is intended to
additionally assign a
supplemental channel to transmit data, the timing generator X40 properly sets
a frame
offset of the supplemental channel such that the supplemental channel should
have the
different frame offset from the frame offset of the presently assigned
fundamental channel
in the traffic state. The FCH DCCH frame offset value and the SCH frame offset
value
are received with the channel assignment message transmitted from the base
station. The
FCH/DCCH frame offset value is transmitted with a fundamental channel
assignment
2~ message, and the SCH frame offset value is transmitted with a supplemental
channel
assignment message. The channel assignment messages are provided to a message
processor ~ 10, and the channel assignment messages processed by the message
processor
510 are provided to a resource controller X20. The resource controller 520
outputs a set
frame offset value for the fundamental channel (FCH/DCCH) and a set frame
offset value
for the supplemental channel (SCH). The frame offset values for the
fundamental channel
and the supplemental channel are provided to the timing generator X40.
The first symbol combines 5~0 combines the multi-path symbols on the
fundamental channel/dedicated control channel (FCH/DCCH), and the second
symbol
3~ combines ~~~ combines the multi-path symbols on the supplemental channel
(SCH). The
first deinterleaver 43l deinterleaves the combined symbol output from the
first s~~rnbol
combines ~~0 in a frame unit in response to the first frame boundary signal on
the control
line 565, and the second deinterleaver 43~ deinterleaves the combined symbol
output
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from the second symbol combiner »~ in a frame unit in response to the second
frame
boundary signal on the control line X60.
FIG. 6 shows a detailed diagram of the timing generator X40 of FIG. ~. The
timing generator X40 includes nvo delays 620 and 630 to generate frame
boundary signals
using the system time X30 and the frame offsets 610 and 640. The frame offsets
610 and
640 include the frame offset 610 for the fundamental channel (FCH/DCCH) and
the
frame offset 640 for the supplemental channel (SCH). The frame offsets 610 and
640 are
provided from the resource controller 520 shown in FIG. ~. The delay 620
delays the
system time 530 by the frame offset 610 set by the resourced controller 520.
That is, the
delay 620 delays the system time X30 by the FCH/DCCH frame offset 610 provided
from
the resource controller X20 and outputs the FCH/DCCH frame boundary signal
56~. The
delay 630 delays the system time X30 by the frame offset 640 set by the
resourced
controller 520. That is, the delay 630 delays the system time X30 by the SCH
frame offset
640 provided from the resource controller X20 and outputs the SCH frame
boundary
signal X60. As described above, in the embodiment of the present invention,
the timing
generator 540 includes the two additional delays 620 and 630 so that the
fundamental
channel and the supplemental channel have the different frame offsets. The
delays 620
and 630 perform delay operations using their unique frame offsets 610 and 640,
respectively. That is, the embodiment of the present invention additionally
includes the
delay for the supplemental channel in order to designate the frame offset
assigned for the
supplemental channel.
FIG. 7 shows a general call setup procedure in a CDMA communication system.
2~ Specifically, FIG. 7 shows a message exchange procedure between modules in
the mobile
station and modules in the base station.
Referring to FIG. 7, the mobile station includes a message processor SIG for
processing a channel establishment-related control message and a resource
controller
(RC) for managing and controlling base station resources. A structure of the
base station
is similar to the structure of the mobile station. That is, the base station
also includes a
message processor SIG for processing a channel establishment-related control
message
and a resource controller (RC) for managing and controlling logical and
physical
resources of the mobile station.
Now, the call setup procedure will be described with reference to FIG. 7. When
the mobile station has user data to transmit, the resource controller sends a
call setup
request signal Call_Setup.Req to the message processor SIG in step 710. The
message
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processor SIG then sends an origination message (or call setup request
message) to the
base station in step 712.
Upon receipt of the origination message transmitted from the mobile station,
the
message processor SIG in the base station inquires of the resource controller
in the base
station whether it is possible to setup the call requested by the mobile
station, in step 714
(Call_Setup.Ind). If it is possible to setup the call, the resource controller
sends a channel
assignment approval signal Call-Setup.Res to the message processor SIG in step
716. The
message processor SIG then sends an eltended channel assignment message for
approving assignment of the requested channel to the mobile station in step
718.
Upon receipt of the extended channel assignment message from the base station,
the message process SIG in the mobile station sends a call setup confirmation
signal
Call_Setup.Conf to the resource controller in step 720. thereby completing
establishment
of the forward and reverse fundamental channel/dedicated control channel.
After completing establishment of the fundamental chamzel between the base
station and the mobile station in the above process, the mobile station and
the base station
perform a service negotiation process in step 722. If the base station and the
mobile
station come to an agreement on a service configuration record in the service
negotiation
process, the message processor SIG of the base station sends the agreed record
value with
a service connect message to the mobile station in step 724. Further, the
service connect
message also includes a non-negotiation service configuration record. The non-
negotiation service configuration record is registered in a non-negotiation
service
configuration record field assigned to the service connect message. In this
process, the
resource controller of the base station designates a frame offset of the
supplemental
channel to be used until a renegotiation is made later with the mobile
station, and registers
the designated frame offset value in the non-negotiation service configuration
record field.
In step 726, the message processor SIG of the mobile station sends to the
resource
controller a Call-Setup.Conf signal indicating that the frame offset of the
supplemental
channel has been set. In addition. the message processor of the mobile station
sends a
service connect completion message to the base station in step 728, thereby
completing
the call setup procedure.
The non-negotiation service configuration record can be transmitted with the
service connect message or a universal handoff direction message, not only
when a call is
initially setup, but also when a new service is connected or a service
configuration is
changed, or when a handoff is performed. Therefore, the embodiment can newly
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designate the frame offset of the supplemental channel in a state other than
the call setup
state.
FIG. 8 shows a detailed procedure for setting a frame offset of the
supplemental
channel, performed in the resource controller, shown in FIG. 7. More
specifically, FIG. 8
shows a procedure for designating a frame offset for the supplemental channel
during a
call setup process or a new service connect process according to an embodiment
of the
present invention. That is, FIG. 8 shows a procedure for setting a frame
offset for the
supplemental channel during a call setup process or a new service connect
process
according to an embodiment of the present invention.
In FIG. 8, operations of steps 810-818 are performed by the base station (BS),
and operations of steps 820-828 are performed by the mobile station (MS).
Further. the
procedure for assigning the frame offset for the supplemental channel
performed by the
I S base station in steps 810-818 corresponds to a procedure performed in the
service
negotiation process of step 722 of FIG. 7. Further, the procedure for
assigning the frame
offset for the supplemental channel performed by the mobile station in steps
820-828
corresponds to a procedure performed after the mobile station receives the
service
connect message from the base station in step 724.
Upon receipt of a call setup request message or a new seance request message
from the mobile station, the base station determines whether it is possible to
assign the
reverse or forward supplemental channel. When determined to perform an initial
call
setup, additional traffic transmission or service connection, the base station
sends a
chamlel assignment message in steps 810 and 812. Thereafter, a traffic channel
is
established or a new service is additionally connected between the base
station and the
mobile station. At this moment, the base station negotiates information for
the call setup
or the new service connection with the mobile station.
After completing the service negotiation in step 812, the base station
determines
the non-negotiation service configuration record constituting the service
connect message
to be transmitted to the mobile station, in step 814. That is, the base
station sets the non-
negotiation service configuration record to be added to the service connect
message in
step 814. At this point, the base station determines through the resource
controller
whether to newly designate a frame offset of the supplemental channel added in
the
present invention. If it is determined to designate a new frame offset to the
supplemental
channel in step 814, the base station determines a proper frame offset taking
into
consideration the setup call, the traffic feature of the newly connected
service and the
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base station resources. The frame offset of the supplemental channel can be
set to be
either identical to or different from the frame offset of the fundamental
channel. Here, the
frame offset of the supplemental channel can be either previously set or
generated by the
base station through a separate operation. In the frame offset designation
process, the
resource controller should set a proper frame offset value such that the loads
are properly
dispersed to transmit the data without delay. Such determined frame offset of
the
supplemental channel is provided to the message processor SIG and registered
in the non-
negotiation service configuration record field. The above operation of
determining the
frame offset of the supplemental channel and registering the determined frame
offset of
the supplemental channel in the non-negotiation service configuration record
field is
performed in step 816. The registered frame offset for the supplemental
channel is set as a
frame offset value of the supplemental channel to be assigned later.
Meanwhile, in step
818, the message processor SIG of the base station sends the service connect
message
including the set negotiation service configuration record and non-negotiation
service
configuration record to the mobile station.
If the base station sends the service connect message for the call setup or
the new
service connection, the message processor SIG of the mobile station receives
the service
connect message in step 820. Upon receipt of the service connect message, the
message
processor SIG analyzes the received service connect message and pro~-ides the
analyzed
results to the resource controller of the mobile station, in step 822. That
is, in step 822, the
message processor SIG analyzes the non-negotiation service configuration
record as well
as the other service configuration record (negotiation service configuration
record).
Further, in step 822, the message processor SIG sends the analyzed results of
the non-
negotiation service configuration record, i.e., information about whether the
frame offset
of the supplemental channel is designated, and the set frame offset value to
the resource
controller.
Upon receipt of the analyzed results, the resource controller determines in
step
824 whether the frame offset of the supplemental channel is registered in the
non-
negotiation service configuration record field. If it is determined that the
frame offset of
the supplemental channel is registered in the non-negotiation service
configuration record
field, the message processor SIG proceeds to step 826, and otherwise, proceeds
to step
828. In step 82G, the resource controller assigns the frame offset for the
supplemental
channel, provided from the message processor SIG, to the corresponding
supplemental
channel, or stores the provided frame offset to use it when it is necessary to
assign the
supplemental channel or use it in response to a supplemental channel request
message
(SCRM) from the mobile station. Finally, in step 828, the mobile station sends
a service
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connect completion message, to thereby end the frame offset setting process.
As stated above, when the base station needs to assign a supplemental channel
after registering the frame offset of the supplemental channel or has received
the
supplemental channel request message (SCRIvI) from the mobile station, the
base station
can use the registered frame offset.
As described above, the embodiment of the present invention designates an
exclusive frame offset for the supplemental channel, being different from the
frame offset
of the fundamental channel, to assign the supplemental channel, thereby making
it
possible to the scheduling loss which may caused by an excess of the link
capacity.
On the other hand. a handoff may occur while data is transmitted over the
supplemental channel assigned according to the embodiment of the present
invention.
1 ~ Therefore, the handoff is possible when an exclusive frame offset for the
supplemental
channel is different from the frame offset of the fundamental channel, as
provided in the
present invention. In the context of the present invention, consideration is
thus given to
a case where it is not possible to support a frame offset value for the
presently used
supplemental channel, because a target base station uses a frame offset value
for the
existing supplemental channel when the handoff occurs. In this situation, it
is not possible
to continuously provide the service.
Therefore, in an embodiment of the present invention, when a supplemental
channel is handed off or newly assigned in a handoff state between the base
station and
the mobile station of the CDMA communication system, a source base station
measures
loads of the respective frame offsets for a target base station, to designate
or reset a
mutually proper frame offset for the supplemental channel. To this end, in the
CDMA
communication system according to an embodiment of the present invention, the
frame
offset for the supplemental channel is designated as a frame offset value
different from
the frame offset of the presently used fundamental channel or different from a
predetermined frame offset in a handoff state between the base station and the
mobile
station. The base station then sends to the mobile station new frame offset
designation
inforn~ation with a universal handoff direction message. Upon receipt of frame
offset
information from the base station, the mobile station can additionally
designate a frame
offset for the supplemental channel in addition to the frame offset for the
fundamental
channel, or can operate a frame offset value different from the previously
designated
frame offset for the supplemental channel.
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Now, a detailed description of a handoff procedure will be made with reference
to the accompanying drawings, to bring a better understanding of the present
invention.
FIG. 9 shows a general handoff procedure in a CDVIA communication system.
Specifically, FIG. 9 shows a message exchange procedure between modules of the
mobile
station and module of the base station.
Referring to FIG. 9, the mobile station includes a message processor SIG for
processing a channel establishment-related control message and a resource
controller
(RC) for managing and controlling base station resources. The base station
also includes a
message processor SIG for processing a channel establishment-related control
message
and a resource controller (RC) for managing and controlling logical and
physical
resources of the mobile station. Here, the base station includes a source base
station
presently in service and a target base station to which the mobile station is
to be handed
1 S off.
Now, the handoff procedure will be described with reference to FIG. 9. Upon
detecting a pilot channel having a new pseudo-noise (PN) value, the resource
controller of
the mobile station reports measured pilot strength to the message processor
SIG and
commands the message processor SIG to send a new pilot strength measurement
message
or extended pilot strength measurement message, in step 1110. Upon receipt of
this
command, the message processor SIG sends a pilot strength measurement message
to the
base station in step 1120.
Upon receipt of the pilot strength measurement message transmitted from the
mobile station, the message processor SIG in the source base station
determines in step
1130 whether to add the mobile station to a new active set based on the pilot
strength
measurement value provided to the resource controller of the source base
station from the
mobile station. If it is determined to add the mobile station to the active
set, the resource
controller of the source base station inquires of the resource controller of
the target base
station whether it is possible to assign a handoff resource to the resource
controller of the
target base station, in step 1140 (HandoffReq). One of the factors for
determining
whether it is possible to assign the resource may include supplemental channel-
related
contents. If the target base station can accept the handoff. the resource
controller of the
target base station sends a handoff acceptance response Handoff Conf to the
resource
controller of the source base station, in step 1150.
Upon receipt of the handoff acceptance response Handoff.Conf from the target
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base station, the source base station sends a universal handoff direction
message including
the new active set to the mobile station in step 1160. Here, if the target
base station
approves the handoff, the source base station forms a new physical channel.
However, an
actual part for generating the message is a message processor SIG of the
source base
station, and the generated message is transmitted to the mobile station using
physical
layers of the source and target base stations, not shown in FIG. 11. Such
generated and
transmitted universal handoff direction message includes supplemental channel-
related
information when a supplemental channel is newly assigned or handed off.
When determining in step 1140 whether it is possible to perform the handoff,
the
resource controller of the target base station examines whether it is possible
to hand off
the reverse or forward supplemental channel. In this process, the frame offset
re-
designation procedure is added during a handoff according to an embodiment of
the
present invention. The re-designation procedure is a procedure included in the
Handoff.Req and Handoff.Conf messages, and a frame offset part must be added
to a
supplemental channel-related factor in the Handoff.Req message transmitted to
the target
base station. If the target base station accepts the same frame offset as the
frame offset of
the supplemental channel presently in service, it is possible to soft-handoff
the
supplemental channel without re-designation of the frame offset. However, when
the
service (or source) base station does not operate with the same frame offset
as presently
used one, the target base station negotiates an acceptable frame offset for
the
supplemental channel with the source base station, so that the source and
target base
stations newly designate the same frame offset, thereby performing a hard
handoff. The
added procedure is a procedure for setting a new frame offset. This procedure
will be
2~ described in detail with reference to FIG. 10.
In step 1170. the message processor SIG of the mobile station sends a control
signal Handoff.Req to the resource controller of the mobile station, and
assigns a
transmission channel or a reception channel of the corresponding fundamental
channel
and the supplemental channel. After completing assignment of the resource
necessary for
the handoff, the resource controller informs the service option which is an
application
service layer of the mobile station, that it is possible to transmit/receive
data. in step 1180
(Handoff.Conf). Finally, in step 1190, the message generator SIG sends a
handoff
completion message to indicate completion of the handoff procedure. Here. the
handoff
completion message is processed by the message processor of the source base
station.
After completion of the above procedure, the base station and the mobile
station exchange
the data traffic with the handoff related base station through the fundamental
or
supplemental channel.
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FIG. 10 shows a procedure for assigning a frame offset for the supplemental
channel according to an embodiment of the present invention, performed during
the
handoff procedure of FIG. 9. In FIG. 10, operations of steps 1210-122-1
correspond to the
operations of steps 1130-110 in FIG. 9 and are performed by the source and
target base
stations. Further, operations of steps 1226-1236 correspond to the operations
of steps
1170-1190 in FIG. 9 and are performed by the mobile station. The procedure for
assigning
the frame offset for the supplemental channel by the source and tarot base
stations is
performed through the steps 1140-11 ~0 of FIG. 9, and the procedure for
assigning the
frame offset for the supplemental channel by the mobile station is performed
through the
steps 1170 and 1180 of FIG. 9.
When the mobile station sends a pilot strength measurement message (PSMM) in
step 1210, the resource controller of the source base station determines in
step 1212
I ~ whether to add a pilot having the newly added PN value to the active set,
depending on
the pilot strength. If it is determined not to add the pilot to the active
set, the resource
controller proceeds to step 1214 to avoid performing the handoff. However, if
it is
determined to add tile pilot to the active set, the resource controller
determines in step
1216 whether the supplemental channel and other resources are presently
assigned. If the
supplemental channel is not assigned, the resource controller hands off only
the
fundamental channel or the dedicated control channel in step 1220. Otherwise,
when the
supplemental channel is assigned in step 1216, the resource controller
proceeds to step
1218 and determines whether it is possible to hand off the supplemental
channel. At this
point, it is necessary to inquire of not only the source base station but also
the target base
2~ station whether it is possible to assign the handoff resource for the
supplemental channel.
If it is not possible to hand off the supplemental channel, the resource
controller hands off
only the fundamental channel or the dedicated control channel in step 1220.
Otherwise, if
it is possible to hand off the supplemental channel, it is necessary to search
the frame
offset having the lower load in both the source and target base stations.
Therefore, in step 1222, the resource controllers of the source and target
base
stations designate a frame offset for the supplemental channel, inform the
message
processor SIG of the designated frame offset, and also, inforn the physical
layers of the
source and target base stations of the frame offset for the cor-esponding
supplemental
3~ channel. Here, if the target base station accepts the same frame offset as
the frame offset
of the supplemental channel presently in service, it is not necessary to re-
designate the
frame offset. However, if the target base station does not operate with the
same frame
offset, the target base station negotiates an acceptable frame offset for the
supplemental
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channel with the source base station, so that the source and target base
stations newly
designate the same frame offset. The physical layer then sets this value as an
exclusive
frame offset value for the supplemental channel. Here, the frame offset of the
supplemental channel established for data transmission can properly be
designated
according to an amount (or load) of the transmission/reception data for the
respective
frame offsets. The frame offset of the supplemental channel can be set to be
either
identical to or different from the frame offset of the fundamental channel.
Here, the frame
offset value is properly determined such that the loads of the service base
station and the
target base station, which designated the frame offset, are properly dispersed
to transmit
the data without delay. Thereafter, in step 1224, the resource controller of
the source base
station directs the universal handoff direction message (L'HDM) to be created,
to which
frame offset-related fields for the supplemental channel are added. Upon
receipt of the
direction, the message controller SIG of the source base station generates the
corresponding message and sends the generated message to the mobile station
through the
physical layers of the source base station and the target base station.
Upon receipt of the universal handoff direction message from the base station,
the message processor SIG of the mobile station analyzes the received
universal handoff
direction message and provides the analyzed results to the source controller
of the mobile
station, in step 1226. After completing the analysis, the resource controller
determines in
step 1228 whether the supplemental channel is included, based on analyzed
results. If the
supplemental channel is included, the message processor SIG sends to the
resource
controller information about whether the frame offset for the supplemental
channel is set,
and the offset value, together with other supplemental channel parameters. The
resource
controller then receives the analyzed results by the message processor SIG and
determines in step 1230 whether the frame offset of the supplemental channel
is
designated or not. If the frame offset of the supplemental channel is
designated, the
resource controller sets the corresponding frame offset value for the
supplemental channel
and sends to the physical layer the new frame offset value together with the
supplemental
channel assignment signal, in step 1232. Upon receipt of the supplemental
channel-related
signal from the resource controller, the physical layer assigns the
supplemental channel
and additionally sets a frame offset value for the supplemental channel to
enable data
transmission/reception. When the forward/reverse supplemental channel is
established
between the base station and the mobile station as stated above, the resource
controller
performs a handoff on the established supplemental channel in step 1234.
However, if it is
determined in step 1228 that the supplemental channel is not included, the
resource
controller performs a handoff on the fundamental channel/dedicated control
channel in
step 1236. Meanwhile, after completion of the handoff, the resource controller
sends a
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handoff completion message (HCM) in step 123, and thereafter, the data traffic
of the
application service is transmitted.
In the embodiment of the present invention. the base station includes a step
(a) in
which the resource controller of the base station determines whether it is
possible to set
the supplemental channel; a step (b) in which if it is determined to set the
supplemental
channel, the resource controller checks a frame offset SCH-frame offset to be
exclusively used for the supplemental channel; a step (c) in which the
resource controller
adds the frame offset to the supplemental channel assignment message to make a
message
shown in FIG. 11, in order to send the frame offset to the mobile station; and
a step (d) in
which the resource controller designates the frame offset value designated by
the physical
layer to the assigned supplemental channel. Here, in the step (d), the
resource controller
should set a proper value such that the loads should be properly dispersed to
transmit the
data without delay.
In addition, the mobile station includes a step (a) for detecting a frame
offset for
the supplemental channel in the process of analyzing the extended supplemental
channel
assignment message and providing the detected frame offset information to the
resource
controller; a step (b) in which the resource controller provides the set value
to the physical
channel; and a step (c) in which the physical layer newly sets the frame
offset during
assignment of the supplemental channel.
FIG. 11 shows a structure of an extended supplemental channel assignment
message or a universal handoff direction message, to which a non-negotiation
service
configuration record field is added according to an embodiment of the present
invention.
In the extended supplemental channel assignment message or the universal
handoff direction message as shown in FIG. 11, the non-negotiation service
configuration
record field includes a REV_SCH ID field indicating an identification (ID) of
a channel
assigned the mobile station during assignment of the reverse supplemental
channel, a
REV_SCH_FRAME_OFFSET_INCL field indicating whether to newly designate a
frame offset during assignment of the reverse supplemental channel, and a
REV_SCH_FRAME_OFFSET field for actually designating a new frame offset. The
non-
negotiation service configuration record field further includes a FOR SCH ID
field
indicating an identification (ID) of a channel assigned the mobile station
during
assignment of the forward supplemental channel, and
FOR_SCH_FRAME_OFFSET_INCL and FOR-SCH-FRAME-OFFSET fields
indicating whether the frame offset is designated during assignment of the
forward
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supplemental channel and the designated value, respectively. In the existing
system, every
channel is assigned the same value as the initially assigned frame offset even
in the
handoff state. However, in the embodiment of the present invention, the
REV SCH_FRAME OFFSET and FOR SCH FRA1VIE_OFFSET field values are
designated such that one of 16 frame offsets should be designated within 20ms
during
assignment of the supplemental channel, thereby making it possible to
designate the
frame offsets in a unit of 1.2~ms. The physical layer designates the frame
offset of the
supplemental channel tlu-ough the above message. Conventionally, the physical
channel
registers the frame offset value of the supplemental channel in the
REV_SCH_FRAME OFFSET, and FOR SCH FRAME-OFFSET fields, and this value
is changed in a unit of 20ms to a REV MULTI FR.~1~IE OFFSET or
FOR_MULTI FRAME OFFSET field value according to the multi-frame size of the
supplemental channel designated in the service configuration record determined
during
service negotiation. In the embodiment of the present invention, the record
value is
changed in a unit of 1.2~ms in order to change the frame offset value every
1.2~ms during
assignment of the supplemental channel.
As described above, the present invention is applied to a case where the
future
CDMA communication system assigns a supplemental channel when data traffic is
generated in a traffic state where a basic call is connected. By providing the
novel
apparatus and method for designating a new frame offset for the supplemental
channel to
fixedly assign the supplemental channel to the user, it is possible to reduce
the
transmission delay and the scheduling loss, which may be caused by traffic
concentration
on a specific frame offset because the traffic has the burst property in the
data service.
While the invention has been shown and described with reference to a certain
preferred embodiment thereof. it will be understood by those skilled in the
art that various
chances in form and details may be made therein without departing from the
spirit and
scope of the invention as defined by the appended claims.
